Enhanced strength-ductility synergy of bimetallic laminated steel structure of 304 stainless steel and low-carbon steel fabricated by wire and arc additive manufacturing

Abstract

Wire and arc additive manufacturing (WAAM) has received increasing attention due to its low cost and high productivity compared to traditional techniques for manufacturing high strength steels. In the present work, WAAM was used to fabricate bimetallic laminated steel structure (BLSS) with enhanced strength-ductility synergy by alternately depositing 304 stainless steel (304 SS) and low carbon steel (LCS) on Q345 substrate. The microstructure and mechanical properties of additive manufactured BLSS were investigated in detail. The 304 SS layer is composed of martensite, different from the vermicular ferrite distributed in the austenite matrix of the single-304 SS structure. While the LCS layer has no obvious change compared to the single-LCS structure, except for the refinement of the blocky ferrite. Meanwhile, fine grains formed at the interface between the LCS and 304 SS layers. The differences in element content, phase constituent and grain size between different layers lead to changes in the mechanical properties of this BLSS along different loading directions. The tensile strength and elongation in the longitudinal (Y) direction reached 999.8 MPa and 28.2%, respectively, where the strength was almost twice that of single-material 304 SS and LCS structure with the elongation between them. Digital image correlation (DIC) was used to observe the strain distribution of the BLSS during tensile process, and a significant stress concentration was observed in the transversal (Z) direction, resulting in a decrease in its tensile properties compared to the Y direction. Fracture topography analysis of specimens with different loading directions revealed a brittle-ductile mixed fracture mode. Our work provides a feasible and flexible method for the fabrication of BLSS with superior mechanical properties, which have potential applications in fields such as architectural and civil engineering structures.